Vitamin C is a six carbon compound structurally related to glucose. The term “vitamin C” is commonly used to refer to two compounds: L-ascorbic acid, which is a strong reducing agent, and its oxidised form, L-dehydroascorbic acid:
Both forms have biological activity and are interconvertible by an oxidation/reduction reaction (Basu, T. K. and Dickerson, J. W. T. (1996) In: Vitamins in Human Health and Disease, Cab International, Oxford, UK, pp125-147).
Vitamin C is important in the synthesis of collagen, neurotransmitters and carnitine, in the absorption of non-heme iron, and as an enzyme cofactor. Vitamin C plays a major role as an antioxidant and free-radical scavenger and is involved in the detoxification of many foreign compounds. It is also essential in the metabolism of folic acid (Basu, T. K. and Dickerson, J. W. T. (1996) In: Vitamins in Human Health and Disease, Cab International, Oxford, UK, pp125-147).
Vitamin C is not produced in the human body. Humans rely on dietary intake of vitamin C for their needs. Vitamin C is by far the most consumed dietary supplement. It acts as an antioxidant; prevents colds and boosts immunity; promotes wound healing; protects against effects of stress; and even prevents or assists in the treatment of cancer. (G. Block, American Journal of Clinical Nutrition, 1991, 54(6 Suppl):1310S).
However, vitamin C can be unstable in the presence of UV radiation and oxygen. The functional group in vitamin C that is responsible for the instability is the same functional group that is responsible for its beneifical effect, i.e., keto-2,3-enediol moiety. Therefore, there is a need for prodrugs of vitamin C to stabilize the keto-2,3-enediol functional group and to revert to the 2,3-enediol when the anti-oxidant activity of vitamin C is desired.